The present invention relates to a non-stick rubber liner. More specifically, the present invention relates to a rubber liner for tanks, pipes, process vessels, and the like for preventing build-up of solid materials; for example, gypsum build-up in the production of phosphoric acid.
Heretofore, teflon as well as oils, such as castor oil, have been used in various applications, but not as an intimate mixture with a rubber compound whereby a non-stick rubber liner is produced.
For example, U.S. Pat. No. 2,017,593 relates to the application of an oil to a rubber surface to reduce the adhesion of ice to the surface. It is not pertinent in that the oil is applied in combination with other oils to the surface of the rubber and, thus, is not intimately mixed therewith.
U.S. Pat. No. 2,681,324 relates to the application of a liquid polytetrafluoroethylene coating. Generally, this patent states that it is difficult to apply a film thickness in excess of 2.5 mills without having the coating crack. This patent allegedly solves this problem by forming a coating containing an aqueous dispersion of colloidal polytetrafluoroethylene particles in a mixture containing a modifying polymeric material and also containing a wetting agent. Table I of the specification sets forth some modifying materials, such as for example styrene-butadiene rubber. However, exceedingly high amounts, for example in excess of 60 percent of Teflon, are required. Moreover, not all modifying polymers work, see Example 14 wherein a styrene-butadiene copolymer was utilized. This patent is not pertinent in that it relates to aqueous dispersions of polytetrafluoroethylene containing a wetting agent and a high amount of a polymeric material.
U.S. Pat. Nos. 2,705,691 and Re. 24,856, are virtually identical. They relate to lamination or coatings of fluorine-substituted polyethylene with other substances. Generally, the joinder of the fluorine-substituted polyethylene to a substance is through a primed surface which may consist of a mixture of Teflon and a butyl rubber. This patent is not pertinent in that it relates to an adhesive bond, to an adhesive bond which contains high amounts of teflon (i.e., 50 percent or greater), to an adhesive binder, and thus not an outer layer, and completely fails to suggest the use of an oil.
U.S. Pat. No. 3,148,234 relates to a method of preparing filaments containing polytetrafluoroethylene emulsion along with a matrix polymer such as polystyrene, polybutadiene-styrene copolymers, polyisobutylene, and the like. In order to produce a fiber, an aqueous dispersion of polytetrafluoroethylene is made along with the polymer matrix. Thus, a wetting agent is also required. The matrix material in the produced fiber can be withdrawn by adequate means such as by heat destruction or extraction. Thus, the patent does not relate to a rubber liner, but rather to a fiber wherein the polymer matrix is preferably destroyed.